And if you run it with a debugger, can you tell us where it crashed and
possibly provide a backtrace?

We might have some win64 socket related problems left in libcurl and I _know_
for a fact that libssh2 has such problems. I've addressed the most obvious one
(a bad API using 'int' for the socket) in the libssh2 git tree only so it
won't be out until next libssh2 release and then we need to make sure libcurl
uses that new API which then won't happen in a release version until a release
after the next libssh2 release...